Notes: Making a Dichotomous Key

Transcription

1 Notes: Making a Dichotomous Key Georgia Performance Standard S7L1 o S7L1a o Students will investigate the diversity of living organisms and how they can be compared scientifically Demonstrate the process for development of a dichotomous key. Essential Questions What are the steps for making a dichotomous key? Continue copying your notes into your notebook where you left off from last week. Make sure you use the front and back of your pages! Steps for Making a Dichotomous Key 1. Observe the pictures or items. 2. List characteristics that you see. 3. Group the items or organisms by characteristics. 4. Write paired opposite statements for each characteristic. For example a. Has Fur b. Does Not Have Fur 5. Create your key in a table format. IMPORTANT RULE There should always be one less step than the total number of organisms to be identified in your dichotomous key. An easy way to remember this rule # of organisms 1 = # of steps in the key So on the sample Dichotomous Key you have on page 45 of your notebook, there are 8 animals so there will be 7 steps, or characteristics in the dichotomous key.

2 Making a Key AN EXAMPLE You have four insects: a ladybug, a housefly, a dragonfly and a grasshopper. What characteristics are present to help you begin your dichotomous key? Set up your Key in a table like this 1. A. 2. A.

3 Step 1 - Dichotomous Key for Organisms Write a pair of descriptive clues for your first characteristic. For this one, our first characteristic will be wing covering. These clues will be written under step 1. Step 2 should consist of a pair of statements that allow for the identification of the insects with wings covered by an exoskeleton. Wings are not covered by an exoskeleton go to step 3 2. A.

4 Step 2 - Dichotomous Key for Organisms Write a pair of descriptive clues for your second characteristic. For this one, our second characteristic will be body type. These clues will be written under step 2. Step 2 should consist of a pair of statements that allow for the identification of the insects with wings covered by an exoskeleton. Wings are not covered by an exoskeleton go to step 3 2. Body Shape A. Body has round shape Body does not have a round shape

5 Step 2 - Dichotomous Key for Organisms Write a pair of descriptive clues for your third characteristic. For this one, our third characteristic will be wing direction. These clues will be written under step 3. Wings are not covered by an exoskeleton go to step 3 2. Body Shape A. Body has round shape Body does not have a round shape 3. Wing Direction A. Wings point from the side of the body Dragonfly Wings do not point from the side of the body Housefly Let s wrap up making a key Remember - there should be one less step than the total number of organisms to be identified in your dichotomous key. Notice that there were four organisms to be identified in this example and it only took three steps. Homework Independent Practice Use a sheet of notebook paper 1. Make a dichotomous key for the Six Kingdoms of Life 2. Refer to the characteristics provided on the Six Kingdom vocabulary sheet in your notebook.